The main purpose of Sam's Remote is for sound effects used for iCarly; the most common ones are applause, booing, and others. According to Freddie in iStart a Fanwar, there are 93 different sounds and Freddie places the sounds that they need for the web show they're going to make that week. The remote is also used for turning on the monitor and making words pop up onto the screen. It has six buttons and six LED's (light-emitting diodes). Each LED lights up according to which button is pushed.
It is widely assumed that the Remote uses Bluetooth technology to transmit information (for example: Button 1 pressed, Button 3 pressed) and Freddie has a program on his computer so that before each show, he is able to assign each button a task (for example: Play Random Dancing) to complete. The best languages to use for this program (if Freddie programmed it himself) would be Assembly, C++, or REALBasic. There are also ready-made programs (AutoHotkey for Windows, built-in system features for Linux and OS X) to play the sound effects when the buttons are pressed, if the remote implements a bluetooth keyboard interface.
Dan Schneider mentioned in various "fun facts" blogs that there is only one remote in existence that has been used ever since the first episode of iCarly.
In the series finale, iGoodbye, Sam gives the remote to Carly when Carly moves to Italy with her father, to remember her by. She said it would be good if Carly ever needed a laugh, a cheer, or some random dancing. This is a sad moment in the series because Sam giving the remote to Carly was a sacrifice for her, and a huge show of friendship. The remote is now Carly's.